There is known a technique of restricting a flow rate of cooling air flowing to a low heat generation component by erecting a flat plate having a through-hole on a substrate on which the low heat generation component and a high heat generation component are mounted.
However, with the technique in the related art as described above, it is not assumed that additional electronic components are to be added later, and it is not possible to add electronic components later. If an electronic component is added later on a substrate on which electronic components (already mounted electronic components) are already mounted, the supply flow rate of the cooling air to the existing electronic components significantly changes due to the addition of the electronic components.
The followings are reference documents.
[Document 1] Japanese Examined Patent Application Publication No. 60-11840 and
[Document 2] Japanese Laid-open Patent Publication No. 58-153398.